Combination core bit



March 23, 1965 E. A. MORLAN 3,174,564

COMBINATION CORE BIT Filed June 10, 1963 2 Sheets-Sheet 1 ERWIN A. MORLAN INVENTOR.

ATTORNEY FIGURE 2 March 23, 1965 E. A. MORLAN COMBINATION CORE BIT 2 Sheets-Sheet 2 Filed June 10, 1963 ERwvN A. MORLAN INVENTOR.

ATTORNEY United States Patent 3,174,554 COillCiBlNATEGN @(ERE BET Erwin A. Morlan, Houston, 'l'em, assignor to Hughes Tool Company, Houston, Tess, a corporation of Betas/are Filed dune it 1963;, Ser. No. 286,631 Claims. {CL 17':'33t3) The present invention relates to core hits, such as are used in obtaining rock specimens from subterranean boreholes. Such bits operate by cutting an annulus in the rock being investigated, thereby forming a rock core which is engaged by a suitable core catcher and carried to the surface. Nearly all such bits are suspended from and rotated by a drill string, and the present invention is directed to a rotary core bit thus employed.

While there are many types of core bits, most may be classified into drag bits and roller bits. Drag bits have cutting structure which is simply rotated about the center of the borehole with the head of the bit and the drill string, whereas roller bits have rollers which are mounted on fixed shafts about which they rotate as the bit rotates and forces the rollers into the bottom of the borehole.

One type of roller bit heretofore known uses rolling cone cutters divided into a set of inside cutters which cut the inside bottom, up to its intersection with the core, and a set of outside cutters which cut the outer balance of the hole bottom, up to the intersection of the bottom with the outer sidewall of the hole. These sets are usually disposed alternately in a circumferential row, and each type generally has hardfacing on the cone gage to maintain a full diameter borehole.

While such rolling cone core bits are quite satisfactory for many purposes, they do not cut a very smooth core. Furthermore, in some of the rocks which are relatively easily shattered, core bits using only rolling cone cutters tend to break the cores quite easily, making it difficult to obtain the sought-for specimens. An additional disadvantage is that such core bits must cut an annulus of considerable width, the result of which is to limit the radius of the core obtainable therewith.

Among the drag core bits, the type most satisfactory for cutting smooth cores with minimum breakage is the diamond bit, i.e., a bit having secured to the head a steel ring or crown or shoe with diamonds embedded in the lower edge, usually in a matrix of tungsten carbide or other wear resistant material brazed or welded to such surface. The chief disadvantage of a diamond bit is its high cost, as even commercial diamonds are quite expensive and have a limited life in this abrasive employment. in addition, a diamond shoe used alone is more subject to breakage in broken formations and unless care is exercised to prevent excessive weight acting on it through the drill string.

The primary object of the present invention is to provide a core bit which combines the best features of heretofore known diamond bits and rolling cone bits. Further objects, considered separately or in various combinations, are to provide a core bit which (1) is capable of cutting a smooth core and with minimum breakage, (2) is less expensive than prior art diamond bits, (3) is capable of cutting rock at the bottom of a hole to define a core of larger radius than that cut by prior art rolling cone bits, and (4) is not subject to breakage with heavy weights or in drilling broken formations.

These objects are achieved in the present invention by the combination of a diamond crown of relatively small annular thickness and a set of rolling cone cutters disposed outside the crown and partially supported thereby, the diamond crown cutting a small annulus immed ately adjacent the core while the rolling cone cutters cut the larger fraction of bottom and maintain gage at the sidewall. Since the radial thickness of the crown is reduced to that necessary for adequate strength, the number of diamonds and hence the cost of the bit is con siderably lower than the cost of a core bit using diamonds as the only cutting means. At the same time, since only the diamonds are used to cut and define the core, smooth cores are obtained with very little breakage.

The construction and advantages of core bits accord ing to this invention will be more readily appreciated from the accompanying drawing illustrating a preferred embodiment, in which:

FIGURE 1 is a longitudinal cross-section of a core bit of the present invention looking in the direction of the arrows 11 of FIGURE 2, except that the rolling cone cutter and bit leg are shown in elevation;

FIGURE 2 is a transverse cross-section looking in the direction of the arrows 22 of FIGURE 1;

FIGURE 3 is a fragmentary longitudinal section showing one rolling cone mounted on its spindle and seated on the diamond crown or shoe at its forward end;

FIGURE 4 is a fragmentary bottom view of the diamond shoe, looking in the direction of arrows 44 of FIGURE 3;

FIGURE 5 is a fragmentary longitudinal section through a rock formation, showing the core and cutting pattern produced in using the bit shown in the other figures; and

FIGURES 6 and 7 are similar to FIGURE 3 but show modified means for seating the cone in the diamond crown.

In the drawing, reference character 10 designates the hollow body of the bit, internally threaded at It for attachment to the lower end of a core-catching device (not shown) or other lowermost member of a rotary drill string. The bore is reduced below the threaded area to define a shoulder 12 through which a multiplicity of flushing fiuid passageways 13 extend longitudinally to the bottom of the body. These passageways 13 have nozzles 1dof wear resistant material secured in their lower ends, and also supply flushing fluid to the diamond shoe 26 through branch passageways 15, annular manifold i9, and longitudinal passages 21 in the shoe. Annular manifold 1% consists of registering semicylindrical grooves in the bit body and the top surface of the shoe.

The reduced bore 16 is tapered at its lower end by the inwardly flaring wall section 17, which is also provided with an annular groove 1-8 opening inwardly and downwardly to receive diamond shoe Ztl. The shoe is in the form of a cylindrical shell with diamonds 22 brazed or welded to the annular bottom surface 24 in a matrix of wear resistant material 23, and also to a portion of both inner surface 2-5 and outer surface 26 just above the bottom. As shown in the drawing, the diamonds 22 protrude slightly from the wear resistant matrix 23, which is interrupted at the lower ends of passageways 21 to define radial grooves 23.

Surrounding shoe 2% and depending from the lower end of bit body 10 is a multiplicity of rolling cone cutter assemblies 39, six such assemblies being used in the particular size embodiment illustrated. As indicated in FiGURE 3, each such cutter assembly comprises a cutter head 31 secured in a recess 8 in hit head 10 and extending downwardly and outwardly therefrom, a bearing pin 32 integral with head 31 and extending inwardly and downwardly toward bit axis 7 and a rolling cone cutter 44 mounted on the bearing pin 32 with rollers 34- and balls 35. These antifr-iction bearing members 34 and 35' are seated in registering races on the outer surface of bearing pin 32 and the inner surface of cone 40, balls 35 also serving to lock the cone against move- Patented Mar. 23, 1965 jment in the axial direction of the bearing pin. Such 'balls are loaded through groove 36, after which ball plug 37 is inserted and welded in place with weld metal 38 to prevent the balls from escaping.

The particular internal bearing structure of cutter assembly 31'} above described and the particular cutting structure on cone 33 form no part of the present invention, but are briefly described herein in the interest of completeness. The cutting structure shown comprises compacts or inserts 39 of wear resistant material suchv as sintered tungsten carbide, such inserts preferably having cylindrical bases and rounded or otherwise blunted protruding tips and preferably being secured in the cone with an interference fit. Such cutting structure is preferable for penetrating the most abrasive high strength rocks, e.g., quartzite, chert, etc., but it should be understood that the older type cutters, having steel teeth integral with. and' projecting outwardly from the cone, may be used for less hard formations. Whatever type of cutting structure is used, the circumferential rows of teeth or inserts are so dispersed from one cutter assembly to the next as to insure full cutting of the bottom annulus between core and sidewall.

At its free end, bearing pin 32 is reduced in size to fonm pilot pin 41. In the preferred embodiment shown, the nose of cone 40 (FIG. 3) bears against the end of pilot pin 41, and is itself severely truncated at end 42 and provided with a pilot or hub 43 in the form of a cylindrical pin which is coaxial with the bearing pin. Outer surface 25 of the diamond shoeis recessed at 27 to permit non-interfering rotation of the cutter, and is also recessed at 29 to provide a bearing socket for the flat end 42 and hub extension 43 of the cone- 'There is a small axial clearance between the adjoining bearing surfaces on cone and shoe to prevent unnecessary drag. In operation, shoe Zll prevents inward bending of the bit leg 31 and movement of the pilot pin 41 transverse its own axis under the influence of formation forces.

Alternative interfits between cutters and diamond shoe are illustrated in FIGURES 6 and 7. Thus the hub may be omitted as indicated by line 44 of FIGURE 6. In the arrangement of FIGURE 7, the cone has a complete opening therethrough, and the pilot pin or a re duced diameter portion thereof extends through the cone and into the corresponding opening 47 in diamond shoe 29. It is preferable to extend this opening and pilot pin completely through the shoe, and secure it thereto with weld plug 46. I

In manufacture, bit body It), diamond shoe 20, and cutter assemblies 39 are separately fabricated, each cutter assembly being assembled by placing a cutter do on a bearing pin 32 :with rollers 34 in place, loading balls.

35 through groove 36, inserting ball plug 37 and welding plug 37 to head 31 with weld metal 38.

.Diamond'crown 20 is inserted in the annular groove 18 of bit body 10 and is secured thereto with a ring of weld metal '9, the semi-cylindricalannular grooves in the two members registering to define annular manifold 19 for the distribution of flushing fluid to passages 21 of the diamond shoe. I V

Each cutter assembly 3d isfitted to the bit' with its head-31 seated in a recess 8 of bit body 10, and also with its nose 'end 42 (and hub 43) seated in the corresponding recess 29 in shoe. 20. To insure proper seating, a dowel pin 6 is fitted into registering drilled holes in both head'31 and body 10, and the assembly is temjunctures of cutter head 31 with bit body 10.

In operation, the assembled bit as described is attached by threads 11 to the outer barrel (notshown) of a complete core eutting-and-retrieval device, and the complete assembly is rotated under suitable weight. The rock pattern cut by the bit described is illustrated in FIGURE 5, which shows that an annulus 51 is cut in the formation to define a central core 50, a hole bottom 52 and a sidewall 53. The portion of the bottom cut by diamond shoe 2% is the lowermost portion 54, which is also closest to core 51?, while the portion cut by the rolling cone cutters is indicated at 55.

While the diamond shoe can be terminated so that it cuts bottom on the same plane or even slightly higher than the rolling cutters, it is preferable to have the diamond shoe lead the rolling cutters, as. shown, because by this construction radial cracks generated by the rolling cutters have greater difiiculty in propagating to the core, and thus core breakage is minimized.

In the embodiment,illustrated the core diameter, equal to the'bore 56 of diamond shoe 26, is 4% inches in. a hole of 8% inches diameter. The radial dimension 54 of the annulus cut by the diamond shoe is /1. inch while the. corresponding radial dimension 55 of the annulus cut by the rolling cutters is 1% inches; It will be noted that of the total 2% inches radial width of the annulus, 78% is cut by the rolling cutters. Since this portion is all towardjthe outside, the area cut by the rolling cutters is an even larger fraction of the total, amount ing to 84%. I The series of small adjacent concavities in portion 55 of the bottom hole pattern of FIGURE 5 indicate the depressions formed as rock is chipped and crushed from the formation by the circumferential rows of inserts 39. As is evident from an inspection of FIGURE 5, these rows of inserts are six in number for the size bit illustrated, and are essentially overlapping. For the size hit illustrated (8%"x 4%), only '2' different cones were found necessary, three cones with one particular compact disposition being alternated with three cones of a second type disposition of compacts. One of these types is identified as 33 in FIGURE 1 and the other as 4d in FIGURE 3, and it will be found from a comparison of these two figures that the nose inserts in the cones of FIGURE 3 cut the bottom depression immediately adjacent the portion'54. cut by the diamond shoe, the. cones shown in FIGURE 1 cutting the next radially outward depression, etc. At extreme portion of the bottom adjacent side wall 53, both types of cutters have a row of inserts to cut this strongest part of the formation and maintain the gage of the hole.

Thus the present invention provides a novel combination of a diamond shoe and rolling cone cutters cooperatively disposed to'form a core bit, the diamond shoe cutting the small portion of bottom adjacent to the core and also forming the radially inward support for the rolling cones, while all of the rolling cones are disposed on bearing pins extending downwardly and radially inwardly from bit legs disposed at the circumference of the bit to 'cut the larger portion of the annulus surrounding the core and acting together to cut the rock at the juncture of the bottom and the sidewall.

I claim:

1. A combination corebit comprising a head having an axial bore, a diamond crown in the form of a cylin- .porarily clamped while welding to form beads 5 at the 7 'drical shell integral and coaxial with said head and depending therefrom, the' lower annular surface of said crown having a multiplicity of diamonds embedded therein and a multiplicity of recesses in its outer surface, and a multiplicity of cutter assemblies integrally attached to said head and dependent therefrom at its periphery, each said cutter assembly including a leg secured to said head, a bearing pin integral with said leg and extending downwardly and 'inwardly toward said axial bore and the outer surface of said crown, and a rolling cone-cutter rotatably mounted on said bearing pin and having its apex end truncated and disposed within one of said recesses. a,

. 2. The combination core bit of claim 1 in which said bearing pin terminates outside the outer surface of said crown. r f 3. The combination core bit of claim. 2jin which said truncated apex end of said coneincludes an integral hub coaxially disposed and extending into said crown, and said crown recess includes a portion accommodating said hub in rotatable relationship therewith.

4. The combination core hit of claim 1 in which said bearing pin extends into said crown, said crown recess includes a portion accommodating the end of said bear- References Cited by the Examiner UNITED STATES PATENTS 1,574,731 2/26 Foster 175-336 X 6 10/29 Phipps 175-335 X 11/30 Slocombe et al 175-335 X 2/33 Brewster 175-332 9/36 Wright 175-332 3/41 Crum 175-332 9/47 Muhlbach 175-332X 1/52 Stokes 175-335 X 12/52 Stokes 175-332 4/53 Stokes 175-332 FOREIGN PATENTS 10/52 Germany. 3/53 Germany.

15 CHARLES E. OCONNELL, Primary Examiner. 

1. A COMBINATION CORE BIT COMPRISING A HEAD HAVING AN AXIAL BORE, A DIAMOND CROWN IN THE FORM OF A CYLINDRICAL SHELL INTEGRAL AND COAXIAL WITH SAID HEAD AND DEPENDING THEREFROM, THE LOWER ANNULAR SURFACE OF SAID CROWN HAVING A MULTIPLICITY OF DIAMONDS EMBEDDED THEREIN AND A MULTIPLICITY OF CUTTER ASSEMBLIES INTEGRALLY ATTACHED TO SAID HEAD AND DEPENDENT THEREFROM AT ITS PERIPHERY, EACH SAID CUTTER ASSEMBLY INCLUDING A LEG SECURED TO SAID HEAD, A BEARING PIN INTEGRAL WITH SAID LEG AND EXTENDING DOWNWARDLY AND INWARDLY TOWARD SAID AXIAL BORE AND THE OUTER SURFACE OF SAID CROWN, AND A ROLLING CONE CUTTER ROTATABLY MOUNTED ON SAID BEARING PIN AND HAVING ITS APEX END TRUNCATED AND DISPOSED WITHIN ONE OF SAID RECESSES. 